About eight months ago, the three-store chain started putting these “quick response” codes in its train ads. When customers scan the little squares with their smartphone cameras, a coffee menu pops up on their screens. Then they can order a cup of coffee on the train—and have it waiting when they arrive at one of Ethical Bean’s shops.

Business has doubled since then, says Chief Executive Lloyd Bernhardt. “We catch people who are on the go and don’t have a lot of time,” he says.

With smartphone use soaring, many small companies are turning to these quick-response, or QR, codes to connect with customers on the go. They’re placing the codes in ads, direct mail, in-store displays and product packaging, and using them to link to a host of features—discounts, websites and videos. And, like Ethical Bean, many companies say they’ve seen a big sales boost.